The present invention relates to improvements to solenoid purge valves for vapor removal devices, where such a valve comprises:
a case provided with a vapor inlet orifice and with a vapor outlet orifice;
an electromagnet coil mounted in said case;
a metal armature of magnetic material situated facing one end of a magnetic core of said electromagnet coil and movable axially between a first position under drive from a return spring in the absence of electromagnet excitation, and a second position under the action of the excited electromagnet, against the return spring;
a valve seat mounted in leaktight relationship with the above-mentioned outlet orifice of the case; and
a closing valve member secured to the above-mentioned moving metal armature, the valve member being pressed against its seat and moved away therefrom when the moving metal armature is respectively in its first position and in its second position.
A preferred although non-exclusive application of such valves lies in devices for recovering the gasoline vapor that accumulates in gasoline tanks, above the liquid phase, and are intended to accompany a controlled-ignition engine, in particular in a motor vehicle, in order to avoid exhausting said vapor directly into the atmosphere.
A valve of the above type is known in which the valve seat is provided directly on the case, in conjunction with said vapor outlet orifice.
Such a valve is being mass-produced at present and is being installed in motor vehicles. That valve gives satisfaction in terms of operation and effectiveness.
However, it suffers from the drawback of being noisy while it is in operation and the noise it makes can disturb the people occupying the vehicle, particularly since modern vehicles generate greatly reduced amounts of background noise while they are in operation.
The noise generated by the solenoid valve is due essentially to the impacts of the moving armature being projected violently against the seat and the core under the control of the electromagnet which is excited by current pulses, e.g. at a frequency of about 10 Hz. These axial impacts are communicated to the case via the seat which is secured thereto and via the coil which is supported by the case. Under the action of these impacts, the case forms a sounding board and transmits the vibration to the environment both through the air and by solid conduction (via the support for the valve case on the vehicle structure).
In spite of it being possible to use a floating mount, vehicle manufacturers also require individual devices to be made quieter so that each device contributes to obtaining as low as possible a noise level in the vehicle cabin.
It is therefore necessary for the solenoid valve itself to be redesigned and improved in order to reduce significantly the vibration of its case, and thus the noise delivered to the environment.
To this end, a solenoid purge valve as mentioned in the introduction is characterized, when embodying the invention, in that said valve seat is supported by the electromagnet coil and has a tubular extension secured thereto which is engaged coaxially in the outlet orifice provided in the case, and which possesses a diameter that is smaller than that of the orifice, an O-ring being interposed radially between said tubular extension and said outlet orifice.
By means of this arrangement, the impacts generated by the moving armature coming into abutment remain concentrated on the coil to which the valve seat has been secured. Furthermore, leaktight contact between the 0ring and both the tubular extension of the valve seat on one side and the outlet orifice on the other side takes place in a direction that is strictly radial, whereas said moving armature comes into abutment in a direction that is axial: the impact that results from this abutment is essentially an axial impact with a transverse (or radial) component that is very small or even zero.
From the point of view of propagating vibration, this provides good decoupling between the case of the valve and the coil with the valve seat secured thereto. This greatly attenuates propagation of the operating noise of the solenoid valve from the case through the air and/or by solid conduction.
In a preferred embodiment, the electromagnet coil comprises:
a hub having two endplates;
an electrical winding mounted coaxially around the hub;
a magnetic core fixed coaxially inside the hub; and
a magnetic circuit surrounding said hub and winding and supported by a first endplate of the hub situated beside said seat;
and the seat is supported by said first endplate of the hub. Under such circumstances, it is advantageous for said first endplate to be provided with a multiplicity of projecting fingers and for the seat to be formed in an strike plate attached to said projecting fingers which can then be implemented so as to be fine in shape. It is also possible to envisage the above-mentioned tubular extension being a projecting portion of the strike plate which surrounds the opening defined at the center of the seat and which extends away therefrom.
In a specific embodiment, the first endplate of the hub has a peripheral support collar in the case, said collar possibly being discontinuous and presenting two diametrically-opposite collar segments. By means of such an arrangement, the electromagnet coil is made easier to install in the case, it is possible to provide keying against wrong installation, and the amount of contact between the coil and the case that supports it is reduced, thereby impeding the transmission of vibration to the case.
In this arrangement, it is also possible to envisage providing for the peripheral collar to be attached to the hub via a plurality of generally radial spokes, with each spoke being, at least in part, thinner than the collar and the hub, so that the thin spokes provide the coil with resilient suspension relative to the case and filter vibration between the electromagnet coil and the case.
It is also possible to envisage the magnetic circuit being generally U-shaped with radial outside fins at the top, which radial fins are secured to said collar, with the end wall of the magnetic circuit being pierced by an opening through which the corresponding end of the magnetic core passes without making contact: this avoids physical contact between the end wall of the magnetic circuit and the magnetic core which is subjected to the abutment impacts of the moving armature, thus likewise reducing the propagation of vibration from the core to the case via the magnetic circuit.
In addition, and still to the same purpose, it is also possible to provide for the end wall of the magnetic circuit to be axially offset from the second endplate of the electromagnet coil so that the vibration of the electromagnet coil is not significantly transmitted to the magnetic circuit via this route.
In a concrete embodiment, the moving metal armature is a small plate having a layer of sealing material secured to one face thereof, thereby constituting the leaktight valve member proper.
Also preferably, the other face of the small plate constituting the moving armature is provided with damping means such as a ring or angularly-disposed studs situated facing the front end of the magnetic core to damp the impact of the moving armature contacting the core.
Advantageously, the magnetic core can be moved axially within the hub for the purpose of adjusting the air gap between the moving metal piece and the facing end of the core.
A solenoid purge valve combining all of the dispositions explained above, or at least most of them, presents effective decoupling of vibration between the vibrating portion and the case, and in the above-mentioned example of application in the motor industry to removing gasoline vapors, a solenoid valve is provided which no longer generates any operating noise that is perceptible within the vehicle.